It is known from EP 0 536 676 A2 for instance that fuel injectors, which dose fuel into the internal combustion engine as a function of a control signal, are provided with a data carrier containing correction values, with which errors in the individual injectors can be equalized.
Provision is made here for the correction data at the end of the manufacture of each fuel injector, which varies from injector to injector as a result of certain manufacturing tolerances and implements the fuel delivery, to be determined and read into the data carrier. Here the data carrier can be embodied as a barcode or as a merely readable storage element. With the first initialization of the control device, this data is then read into a writeable memory of the control device and is used during subsequent operation to control the internal combustion engine.
Modern control devices have different functions, which likewise determine correction values which are to be assigned to an injector. Such a function is referred to as zero quantity calibration for instance. This data is stored in a control device and used to control the internal combustion engine.
The individual injection quantity of a fuel injector is usually detected at several check points within a test bench. The deviation of the respective injection quantity from the target value is determined here. This data is applied in a suitable form to the injector during manufacture of the injector. During engine assembly and/or motor vehicle assembly, the data is transmitted to the control device by way of suitable systems, for instance a diagnostic interface. In this context, methods exist for storing this data, which enable this control device to be replaced if an error occurs. These are known from EP 1 400 674 B1, according to which the classification of data on a storage apparatus, which is arranged directly on the fuel injector, is stored. The available data is used for the zero quantity calibration and/or quantity correction.
The problem frequently occurs here of an individual dosing of the fuel injectors in their overall operating range being needed in order to calculate correction data correspondingly and to indicate this on the fuel injectors. Dosing methods of this type which have been implemented on test benches are very time-consuming and expensive and are thus unsuited to the large-scale production of a large number of fuel injectors.
It should also be noted that fuel injectors are subject to ageing processes, which require the fuel injectors to be adapted to their respective functional states.
In DE 41 34 304 A1, several variables of a solenoid valve of a fuel injection device for an internal combustion engine are also detected in order to easily and rapidly compensate for irregularities during the injection process. Factors are determined on a test bench, which, as stored actuating variable factors, modify a previously calculated actuating variable for controlling the solenoid valve. This modified actuating variable then controls the solenoid valve. The determined factors are selected as a function of previously detected variables such that a selectable operating variable of the internal combustion engine is firstly adjusted, then a determination of an actuating variable, based on the marking arranged on a shaft of the internal combustion engine is calculated, an actual actuating variable is determined separately for this solenoid valve, giving the factor from the calculated actuating variable and the determined actuating variable. Storage of the determined factor and modification of the selectable operating variables are also implemented before these cited steps are repeated correspondingly often until an optimized functional state is established.
An injection system is known from U.S. Pat. No. 4,402,294 A, which implements a fuel injector calibration. A calibration resistor is used for the calibration, said resistor having a resistance which correlates with the fuel flow rate of the injector. The values thus determined are related to a number from a table. This number is then used to determine the time needed to operate the injector such that the desired fuel output is maintained.
It is also known to classify injectors with measurement data determined on a test bench into different groups, in order as a result for instance to obtain a group of injectors with low fuel delivery, a group of injectors with high fuel delivery and a group of injectors without significant deviations from the target values for the fuel delivery. Fuel injectors from just one group are then built into a motor vehicle and the control device is programmed accordingly. A classification of this type has the disadvantage that it combines a large number of injectors within a group still with—even if more minimally—different fuel delivery characteristics, so that even when fuel injectors from a common group are used, there is no optimal coordination of the fuel injectors used in a common motor.